I am developing an application with Sprintboot + REST + Angular. While I am working on the REST API, I am trying to design as RESTful as possible. I'm encountering certain pages where the Angular UI must send multiple requests to the service to display the page like a User Approval page. I'm worried this would slow down the application or create complexity in Angular code base. Should I just have an end point /orderapproval that would do every thing related to order approval functionality or have bunch of APIs that need to be called for like /order /inventory /user etc. It is awful to consider /orderapproval as a REST API. But is it acceptable to just work as an API for applications that have both Back End and UI running in same web server.
To answer your question directly. No, a pure RESTful web service is not required for an angularjs app. It will work just fine with more RPC like interfacing also.
I would never recommend anyone to pursue pure RESTfulness, especially the HATEOAS part is just a waste of time and effort. Noone will work with your API that dynamically. Until you have concrete requirements in this area I would stay far away from it.
I prefer a 'back-end for front-end' strategy, if you need a 'orderapproval' resource cause it would help reduce the amount of chatting with the back-end that would be more then fine.
Building one web app and simultaneously a 'generic general purpose Web API' is a really hard thing to do, I typically recommend customers against this strategy.
The general purpose Web API is really something you should look at separately or something that could emerge after your 3rd app using a common interface.